1. Field of the Invention
The present invention relates to a substrate container in which substrates such as semiconductor wafers are stored in an interior space and conveyed, and more particularly, to a front opening unified pod (FOUP) as a wafer storage pod as which performs opening and closing of a lid on a front side of the pod, and has a replacement function with respect to a clean gas in an interior space thereof.
2. Description of the Related Art
Processing operation on substrates such as semiconductor wafers (hereinafter, simply referred to as “substrates”) includes multiple processing steps. Those processing steps are performed in a clean room which has a certain size and whose cleanliness is ensured. In the clean room, there are arranged processing apparatuses for performing respective processing steps. An interior space of each of the processing apparatuses has cleanliness maintained to be higher than that in the clean room in which the processing apparatuses themselves are arranged. The substrates are stored in a FOUP (hereinafter, referred to as “pod”), and conveyed together with the pod among the processing apparatuses for substrates such as semiconductor wafers, the processing apparatuses satisfying the front-opening interface mechanical standard (FIMS). During the substrates are moved from apparatus to apparatus, by keeping high cleanliness and preventing oxidization in the pod, it is unnecessary to control the environment of the entire of the wide clean room. As a result, it achieves efficient control and management to keep only ambient atmosphere around the substrates (minute volume relative to a volume of the clean room) in the high-cleanliness and oxidization-resistant states.
FIG. 5 illustrates a conventional type of pod 1 that is in a state in which the pod 1 is placed on the processing apparatus 20. Generally, the pod 1 includes a lid member 2 and a pod case (main container) 3. The pod case 3 has an opening 3a formed at one end thereof. The lid member 2 as a door of the pod 1 is capable of closing and sealing the pod case 3 by closing the opening 3a. The pod case 3 includes a shelf 5 arranged therein. The shelf 5 includes multiple stages arranged in pairs in parallel with each other in a vertical direction. Each pair of the multiple stages is generally arranged horizontally, and is capable of holding corresponding one of substrates.
An interior space 20a of the processing apparatus 20 is used in processing steps performed on the substrates. The interior space 20a of the processing apparatus 20 has cleanliness maintained to be higher than ambient atmosphere in a clean room. In the interior space 20a of the processing apparatus 20, there are arranged a transfer robot, a processing device, and the like. The processing apparatus 20 has a wall portion provided with an access opening 20b for access from an outside of the processing apparatus 20 into the interior space 20a of the processing apparatus 20. When a user does not access the interior space 20a of the processing apparatus 20 from the outside, as illustrated in FIG. 5, the access opening 20b is closed by a FIMS door 21 (hereinafter, referred to as “door”). The processing apparatus 20 includes a load port portion 22 for placing the pod 1 thereon. The load port portion 22 functions to place the pod 1 so that the pod 1 faces the access opening 20b. That is, first, when processing steps are performed on the substrates, the pod 1 is placed on the load port portion 22 of the processing apparatus 20. The pod 1 is properly placed On the load port portion 22 of the processing apparatus 20, so that the opening 3a of the pod case 3 of the pod 1 faces the access opening 20b of the processing apparatus 20. After that, the load port portion 22 performs positioning operation of arranging the pod 1 at a predetermined position. Simultaneously with opening and closing of the access opening 20b of the processing apparatus 20, the opening 3a of the pod case 3 of the pod 1 is opened. For example, generally, the door 21 holds the lid member 2 of the pod 1 so as to simultaneously open the access opening 20b of the processing apparatus 20 and the opening 3a of the pod case 3 of the pod 1. In this state, the substrates respectively placed on the pairs of the stages of the shelf 5 are moved in a horizontal direction so as to be taken out from the inside of the pod 1 through the opening 3a. Then, the substrates are transferred into the interior space 20a of the processing apparatus 20. Then, the substrates transferred into the interior space 20a of the processing apparatus 20 undergo the processing steps. After completion of the processing steps, the substrates are returned from the interior space 20a of the processing apparatus 20 into the pod 1 through the opening 3a. In this manner, the substrates are returned to predetermined pairs of stages of the shelf 5 in the pod case 3 in the pod 1.
When all the processing steps on the substrates in the pod 1 are completed, the door 21 of the processing apparatus 20 re-closes the access opening 20b of the processing apparatus 20. With this, the opening 3a of the pod case 3 is sealed by being closed by the lid member 2 of the pod 1, the lid member 2 being held by the door 21. In this stage, atmosphere in the pod case 3 is external atmosphere (ambient atmosphere in the interior space 20a) containing dust and oxygen. Thus, in order to maintain the substrates to be clean until the subsequent steps, it is necessary to remove the dust in the atmosphere and to remove gas components liable to react with surfaces of the substrates (in particular, oxygen (O2)). Therefore, generally, after the lid member 2 closes and seals the pod case 3, the atmosphere in the pod 1 is replaced with an inert gas (hereinafter, referred to as “replacement gas”).
As conventional means for replacing the atmosphere in the pod 1 with the replacement gas, there are various types. For example, Japanese Patent Application Laid-Open No. 2003-17553 and Japanese Patent Application Laid-Open No. 2004-345715 respectively disclose a pod of such a type that the air is supplied and exhausted through a bottom surface of the pod 1. In the pods of this type, as illustrated in FIG. 5, an air-supply port 23 and an exhaust port 24 are arranged in a lower portion of the pod case 3 of the pod 1. When predetermined pipes arranged on a processing-apparatus-20-side are connected to the air-supply port 23 and the exhaust port 24, as indicated by arrows of FIG. 5, the replacement gas is supplied into the pod 1 through the air-supply port 23 and exhausted from the pod 1 through the exhaust port 24.
In one of processing apparatuses, when the lid member 2 closes the pod case 3 after completion of processing steps on substrates, the atmosphere in the pod case 3 is ambient atmosphere in the interior space 20a containing dust and oxygen. Thus, in the pod 1, it is necessary to replace the atmosphere in the pod 1 with the replacement gas so that the dust is not blown up and is prevented from adhering to the substrates. Thus, when the atmosphere in the pod 1 is replaced with the replacement gas, the replacement-gas flow in the pod 1 is required to enter a stable laminar state free from flow disturbance. Further, it is desired that the gas in the pod 1 be completely replaced so that the dust in the pod 1 is discharged to the outside of the pod 1. Still further, it is desired that a state be achieved in which the dust in the pod 1 is constantly removed from the inside to the outside of the pod 1. However, the pod disclosed in each of Japanese Patent Application Laid-Open No. 2003-17553 and Japanese Patent Application Laid-Open No. 2004-345715 is not intended for solution of problems with discharge of the dust in the pod 1 to the outside of the pod 1.
In the pod disclosed in each of Japanese Patent Application Laid-Open No. 2003-17553 and Japanese Patent Application Laid-Open No. 2004-345715, the exhaust port 24 is not provided with a special configuration for removal of dust. Specifically, it is considered that, by setting of back pressure on an exhaust-port-24 side to be relatively lower than pressure on an air-supply-port-23 side, the replacement gas can be exhausted from the inside of the pod 1. However, actually, lowering of the back pressure on the exhaust-port-24 side does not necessarily directly lead to an effect of exhaust of the replacement gas from the inside of the pod 1. In order to exhaust the replacement gas from the inside of the pod 1, it is more effective to increase the pressure on the air-supply-port-23 side.
Note that, when static flow of the replacement gas to the exhaust-port-24 side is formed in the pod 1 by lowering of the back pressure on the exhaust-port-24 side, the dust in the pod 1 can be collected to the exhaust-port-24 side.